Process for obtaining metal printing-plates with silver-salt gelatin emulsion.



P. SCHUMAOHER.

PROCESS FOR OBTAINING METAL PRINTING PLATES WITH SILVER SALT GELATIN EMULSION. APPLICATION FILED DBO.17, 1910.

1,042,827, Q Patented 001;. 29, 1912.

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PETE-B SGEUMACHER, 0F FRANKFORT-ON-EHE- -MAIN, GERMANY, ASSIGNOR TO CORPORATION OF KLIMSCH & 00., 0F FRANKFORT-QN-THE-MAIN, GERMANY.

PROCESS FOR bBTAINING'METAL PRINTING-PLATES WITH SILVEB-SALT'GELATIN Y EMULSION.

Patented 0013.29, 1912-.

Application filed December 17, 1910. Serial No. 597,923.

To all whom it may concern:

Be'it known that-I, PETER SoHUMAoHER,

doctor of philosophy, chemist, a subject of the German Emperor, and resident of Frankfort on the Main, Germany, with post-oflice address Griineburgweg No. 129, have invented new and useful Improvements in Processes for Obtainin Metal Printing Plates, with Silver-Salt elatin Emulsion, of which the following isa specification.

The present invention relates to animprovement in the process of producing printing plates by the medium of silversalt-gelatiu-emulsion.- In the application of such an emulsion directly to metal-plates,.it has been found absolutely necessary to'first produce a protective intermediate layer'on the plate to avoid a decom osition of the silver compounds of the emu sion. For this purpose a stratum of varnish or asphaltum has been proposed but I have found that a layer produced by chemical action by bathing the plate in a solution of suitable acids or salts is preferable, thus obtaining a greater speed, cheapness and simplicity of the process; Especially by treating the plates with a weak solution of chromic acid of say (0.22%) a perfectly dense layer of oxid is produced, but also other acids or salts (oxalic acid, ferrocyanid of potassium a mixture of alum and bichromate of ammonia) producing a close stratum on zinc or copper plates may be used.

After the protective layer is produced, the" emulsion is applied and the sensitive plates after exposure are either treated with a developer hardening the lights of the negative, (for. instance pyrogallic acid) or this hardening is done in a separate operation by treating the developed plate with a solution of bichromates. Now the unhardened portions of the gelatin film are dissolved in warm water and the negative thus obtained is turned. into a positive, by applying fat inks or varnishes which sticlr only to the clear parts of the plates, whlle the rest of the gelatin-film can beremoved by the action of weak solutions of acids and rubbing with a pad of cotton wool orielt. This inversion ofl'ers the difliculty that fat inks or varnishes do not adhere firmly to the intermediate layerand I have found it absok y l 7 m ve the-protective layer, which can be done by weak solutions of acids or acid salts, (for instance nitric or hydrochloric acid, perchlorid of iron, dissolved in water or spirit),"'the= concentration and time of action of'which must be regulated in such manner that the layer is removed without injuring the hardened gelatin. After this operation, inks or varnishes will enter into a firm connection with the metal and the plate can be etched or used for any kind of printing.

In orderto explain exactly the details of the invention, in the annexed .drawing the following different stages of the process are represented.

Figure 1 represents the printing plate withthe protective layer thereon. Flg. 2 represents the same after applying the film of gelatin emulsion. Fig. .3 represents the exposed plate after development and after dissolving the .nnhardened parts, in hot water. Fig. 4 represents the same after the protective layer is removed, Fig. 5 representsthe same after the application of fat inks or varnishes and after the cleaning of the surface of the gelatin film, and'Fig. 6 represents the plate ready for printing or etching after removing the gelatin film.

In the several figures, A represents vthe printing late, B the protective layer, C the filni of ge atin emulsion, and D the fat inks or armshes. i

What I claim is: v

'1. The process of making metal printin plates with gelatin emulsion which consists in treating e plate with a solution of substance givlng an acid reaction, thereby providing-the plate with a protective easily removable, layer, applying the emulsion to said layergexposing and developing the picture, removing the unhardened portlons with .warm water, applying fat inks or varnishes to the plate and removmg the rest of the gelatin v 2. The; rocess of making metal printing plateswith gelatin emulsion which consists in treati the plate with a solution ofsubstance giving an acid reaction, thereby providing the plate with a. protective easily removable layer, appl the emulsion to said layer, exposing d developing the design, removing the u'nhardened portions with warm water, removing "from the printing f 1 7 g Y I portion the protective layer of the em posedl i'eseme of two Witnesses, this sixth day of and developed plate li y thekaotion ox aim ecember 1910, substances, a yi or at in s or varnis es H to the plate a e i moving the rest of the PETER SO 5 gelatin film. Witnesses:-

In testimony, that I claim the foregoing CARL WEmE, as my invention, I have-signed my name in EVA SATTLEB.

CHER 

